As a reading element of a thin film magnetic head, a magneto resistance (MR) element made with a multilayer film has been known. Conventionally, a current in plane (CIP) element, in which a sense current flows in a direction in plane with a film surface, has been primarily utilized. Recently, in order to enable a further high density recording, a current perpendicular to the plane (CPP) element, in which a sense current flows in a direction orthogonal to a film surface, has been developed. As elements of this type, a tunnel magneto-resistance (TMR) element in which a TMR effect is utilized and a current perpendicular to the plane-giant magneto resistance (CPP-GMR) element in which a GMR effect is utilized have been known.
As an example of the GMR element or the TMR element, there is an element including a spin valve film (hereafter, referred to as SV film). The SV film includes a pinned layer where a magnetization direction is pinned with respect to an external magnetic field, a free layer where a magnetization direction is changed with respect to the external magnetic field, and a spacer sandwiched by the pinned layer and the free layer. The SV film is sandwiched by a pair of shields that are electrodes for supplying the sense current.
In accompaniment with a recording density improvement of a recent magnetic recording medium, the thin film magnetic head has a so-called side reading problem in that magnetic information leaked from adjacent tracks is also read. In order to cope with the side reading problem, JP 2005-203063A discloses a thin film magnetic head in which soft magnetic layers are disposed on both sides of a MR element in a track width direction. In the specification, the track width direction indicates a direction parallel to a track width direction of a recording medium when a slider including the MR element faces the recording medium. Since a soft magnetic material absorbs a magnetic flux from the adjacent track, the effect of noise due to the magnetic flux from the adjacent track is suppressed. As a result, it is thought that the thin film magnetic head corresponding to a recording medium of high recording density is provided.
In the thin film magnetic head disclosed in JP2005-203063A, a domain control layer is formed in a SV film in order to form a free layer in a single domain structure. The domain control layer is configured with a non-magnetic separate layer, a longitudinal bias layer, and an antiferromagnetic layer. Or, the domain control layer may be configured with a non-magnetic separate layer and a hard magnetic layer or the like. The domain control layer applies a bias magnetic field to the free layer to form the single domain free layer. Such a single domain free layer has advantages in view of improving linearity of resistance variation corresponding to an external magnetic field variation, and of simultaneously suppressing Barkhausen noise. A magnetization direction of the biased magnetic layer is pinned in the track width direction.
However, in JP2005-203063A, a gap between a pair of shields is increased only by an amount of the thickness of the antiferromagnetic layer or the hard magnetic layer of the domain control layer. Particularly, the antiferromagnetic layer or the hard magnetic layer for generating exchange anisotropy is required to have sufficient thickness. When the gap between the shields is large, a magnetic field from an adjacent bit is likely to be read so that high frequency characteristics of the thin film magnetic head may be deteriorated. When a thickness of the antiferromagnetic layer or the hard magnetic layer is thinned, sufficient bias magnetic field may not be applied to the free layer. Particularly, the antiferromagnetic layer may need to have a film thickness of 6 nm or more.
Therefore, a thin film magnetic head is desired in which the gap between the shields (in other words, a height of the SV film) is suppressed, and in which a sufficient bias is applied to the free layer.